Underwater Autofocus on DVX?

Q

QuickSloth

Active member
I just read that Autofocus does NOT work on camcorders underwater. Is this true?

http://www.rtsphoto.com/html/ewamar.html

I am about to get an underwater bag/housing for a DVX100a marine wildlife doc. I do a great deal of closeups(500D) and, well... my finger rest heavily upon the autofocus assist button.

-Quote-
DOES THE AUTOFOCUS WORK: Yes, above the surface. Underwater, camcorders must be set to manual at the furthest focussing distance. The camcorder will focus anywhere from 8 to 20 feet underwater depending on the clarity of the water. Most SLR Autofocus cameras will work in the AF mode underwater.
-Close Quote-

Alright DVXUSERs tell me they aren't talking about me!
 
I don't know from experience, but it sounds correct. Auto focus uses a dominate image that is in the frame and focuses on it, when your in the water, Im sure the camera will have trouble finding that dominate subject due to the distortions water will have on its imaging.....your AF wil probably just keep racking from far to close focus due to this.
 
I have already used a homemade parascope, consisting of a trash can with plexiglass at the bottom, and as far as I can remember, the autofocus assist seemed to work. These are closeups, with less than 1m to the subject.
 
if you are doing CU's then wouldnt you not require the AF? I would think it would be safer for your shot to use manual focus. or do you plan on having varying distances of your subject in one shot? - even if you do, I still think it will be a safer idea to use manual focus to ensure the right focal lengths.
 
No problems with AF. The viewing angle and the focus range will be slightly changed. Same (optical) story when shooting fishes through the frontglass of an aquarium.
 
I will be using an ewa marine bag, so I will not have access to the focus ring. I don't use autofocus, I use auto focus assist in manual focus mode.

Andre- so you really think AF assist will be no problem? Is rtsphoto.com wrong?
 
You need to be in focus from about 4 inches to infinity at all times underwater to capture whatever presents itself. Use a wide angle lens.
 
Focussing systems based on TTL image analysis (like all videocams do) are perfectly OK. Only cams based on other AF methods (triangulation..) can get fooled. So the rtsphoto.com info is at least incomplete.
 
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